A keratoacanthoma is a benign skin growth that appears most often in elderly people who have fair skin. The growth resembles a squamous cell skin cancer, but it grows more rapidly than a squamous cell cancer. Keratoacanthomas grow rapidly, enlarging by up to 1 to 3 centimeters within a few weeks. They then cease to grow for several weeks to months. The growths then regress and heal while scarring over for the next several months up to 1 year.